A rare atmospheric phenomenon turned the skies in South Dakota green

The citizens of South Dakota might have been forgiven for thinking an alien invasion was in progress yesterday evening as the sky over the midwestern state turned an eerie green color. After everything we've been through recently, an alien invasion is about the only thing that hasn't actually happened yet.

Resembling something out of Stranger Things or even War of the Worlds, the rare atmospheric phenomenon is known as a 'derecho' and almost always precedes a tornado, heavy rain or heavy winds. A wind storm qualifies as a derecho if the trail of damage extends for between 250 miles and 400 miles and has wind gusts of at least 56mph and the one that hit South Dakota picked up wind speeds up to 99mph in some areas. 

The unusual sight captured the internet’s attention after many users shared pictures of the seemingly supernatural sight. Some speculated—in jest— that the recent CERN experiment had unwittingly unleashed a Lovecraftian demon from beyond dimensions.

Twitter user @eddiedevonne remarked on how his pictures had gone viral overnight. And he wasn't the only one to observe the otherworldy event.

According to AccuWeather, as the setting Sun approaches the horizon, colors like red, with longer wavelengths, become increasingly prevalent. The ghostly green color was a result of blue light from storm clouds combining with the red and yellow light of the sunset.

The National Weather Service confirmed that a derecho storm barreled through much of South Dakota, Minnesota and Iowa, leaving nearly 30,000 people without power for hours.